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VulnerabilityPublished Updated

CVE-2026-23401: Linux kernel · Use After Free

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · CVSS 8.1 High · fixed in fd28c5618699180cd69619801e9ae6a5266c0a22 : patch Linux kernel soon.

Data as of 5 Nov 2026, 21:49 UTC

CVSS 3.1 base score
8.1High
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
ADP (redhat-SADP)CVSS 3.18.1
CISA SSVC
Exploitation
No evidence of active exploitation and no public proof of concept
Automatable
Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact
Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-05.

Patch
Available – fixed in fd28c5618699180cd69619801e9ae6a5266c0a22, ed5909992f344a7d3f4024261e9f751d9618a27d, bce7fe59d43531623f3e43779127bfb33804925d +4
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 1 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

ProductAffectedFixed in
LinuxLinuxAffected
  • ≥ a54aa15c6bda3ca7e2f9e040ba968a1da303e24f, < fd28c5618699180cd69619801e9ae6a5266c0a22
Fixed in
  • fd28c5618699180cd69619801e9ae6a5266c0a22
LinuxLinuxAffected
  • ≥ a54aa15c6bda3ca7e2f9e040ba968a1da303e24f, < ed5909992f344a7d3f4024261e9f751d9618a27d
Fixed in
  • ed5909992f344a7d3f4024261e9f751d9618a27d
LinuxLinuxAffected
  • ≥ a54aa15c6bda3ca7e2f9e040ba968a1da303e24f, < bce7fe59d43531623f3e43779127bfb33804925d
Fixed in
  • bce7fe59d43531623f3e43779127bfb33804925d
LinuxLinuxAffected
  • ≥ a54aa15c6bda3ca7e2f9e040ba968a1da303e24f, < aad885e774966e97b675dfe928da164214a71605
Fixed in
  • aad885e774966e97b675dfe928da164214a71605
LinuxLinuxAffected
  • ≥ a54aa15c6bda3ca7e2f9e040ba968a1da303e24f, < 459158151a158a6703b49f3c9de0e536d8bd553f
Fixed in
  • 459158151a158a6703b49f3c9de0e536d8bd553f
LinuxLinuxAffected
  • ≥ a54aa15c6bda3ca7e2f9e040ba968a1da303e24f, < 695320de6eadb75aaed8be1787c4ce4c189e4c7b
Fixed in
  • 695320de6eadb75aaed8be1787c4ce4c189e4c7b

Description

In the Linux kernel, the following vulnerability has been resolved: KVM: x86/mmu: Drop/zap existing present SPTE even when creating an MMIO SPTE When installing an emulated MMIO SPTE, do so *after* dropping/zapping the existing SPTE (if it's shadow-present). While commit a54aa15c6bda3 was right about it being impossible to convert a shadow-present SPTE to an MMIO SPTE due to a _guest_ write, it failed to account for writes to guest memory that are outside the scope of KVM. E.g. if host userspace modifies a shadowed gPTE to switch from a memslot to emulted MMIO and then the guest hits a relevant page fault, KVM will install the MMIO SPTE without first zapping the shadow-present SPTE. ------------[ cut here ]------------ is_shadow_present_pte(*sptep) WARNING: arch/x86/kvm/mmu/mmu.c:484 at mark_mmio_spte+0xb2/0xc0 [kvm], CPU#0: vmx_ept_stale_r/4292 Modules linked in: kvm_intel kvm irqbypass CPU: 0 UID: 1000 PID: 4292 Comm: vmx_ept_stale_r Not tainted 7.0.0-rc2-eafebd2d2ab0-sink-vm #319 PREEMPT Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 RIP: 0010:mark_mmio_spte+0xb2/0xc0 [kvm] Call Trace: <TASK> mmu_set_spte+0x237/0x440 [kvm] ept_page_fault+0x535/0x7f0 [kvm] kvm_mmu_do_page_fault+0xee/0x1f0 [kvm] kvm_mmu_page_fault+0x8d/0x620 [kvm] vmx_handle_exit+0x18c/0x5a0 [kvm_intel] kvm_arch_vcpu_ioctl_run+0xc55/0x1c20 [kvm] kvm_vcpu_ioctl+0x2d5/0x980 [kvm] __x64_sys_ioctl+0x8a/0xd0 do_syscall_64+0xb5/0x730 entry_SYSCALL_64_after_hwframe+0x4b/0x53 RIP: 0033:0x47fa3f </TASK> ---[ end trace 0000000000000000 ]---

References

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